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The social aspects of quantum entanglement

Confessions of a theoretical physicist. Our readers might be wondering how and why an article with such a strange title fits in a journal of popular culture. Actually, the common reaction when people meet a theoretical physicist is to look at him like an alien, or an autistic psychopath unable to conduct a normal life enjoying more ‘popular’ subjects. Well, there are many reasons why theoretical physics is not so popular even among people with a passion for culture. Everybody would be puzzled when hearing the absurdities that we often profess about how Nature works! Quantum theory, specifically, affirms that our everyday experience of the “macroscopic” world (things that we see and touch) is useless to describe how the “microscopic” world (the minuscule components of the same things that we see and touch) behaves. These tiny objects don’t even know whether they are particles (like billiard balls) or waves of energy (like sun rays), and not because we are unable to detect them with enough precision, but because there is an ultimate a priori limit to the knowledge that can be gained. Thus, depending on how we look at them, they behave as particles or as waves, answering randomly to our tests. Now go and tell everybody that the best minds of the last century discovered this (confirmed by over 70 years of experimental evidences): that the world is intrinsically random and it’s impossible to have complete information of its components, and this implies that there are for example poor kittens which are at the same time dead and alive… I guess they will feel a bit depressed, and/or will think that you are completely drunk!! Indeed, quantum theory might come handy! This “uncertainty” principle says that if you know perfectly where a particle is, you cannot know its speed, and viceversa. So next time a policeman stops you saying you’re running too fast with your car, try to tell him (and let us know if it works) that according to a Mr Heisenberg, as you are in a given place there’s no way to know which was your speed; and if he insists that he has recorded your speed, you answer that you couldn’t be in that given place at that moment, as you are delocalized in the entire universe!!! Now, if a couple of brave readers arrived alive at this point, they must have at least a terrible headache! Relax, you are in good company. Mr Einstein eventually refused quantum ideas because “God – he said – does not play dice”. And Mr Feynman (and I’m mentioning all Nobel Prize winners!) honestly said: “Nobody understands quantum mechanics”. So, do I have any hope to make quantum physics a popular piece of culture? I will now tell you something about the most counterintuitive and radical feature of quantum mechanics.. yet I will try to make it as natural as the feeling that everybody experiences from the moment of birth and before: love. Entanglement: passion at a distance.1 Mr Schrödinger (another pioneer of quantum mechanics, and Nobel Prize winner: he promoted the cat example) coined the term “entanglement” (entrelazamiento) in 1935 to describe a peculiar connection between quantum systems: “When two systems enter into temporary physical interaction due to known forces between them, and when after a time of mutual influence the systems separate again, then they can no longer be described in the same way as before. I would not call that one but rather the characteristic trait of quantum mechanics, the one that enforces its entire departure from classical lines of thought. By the interaction the two systems have become entangled.” Entanglement thus manifests as a somehow puzzling correlation (Einstein blamed it as a “spooky action at a distance”) between parties who once came into contact, and mantain their contact even miles away. This has been experimentally demonstrated with individual atoms or light beams: but how can it fit in our everyday experience of life? The closest feeling which comes into my mind is
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more intricate orgies! The quantum society, you see, is not that much different from ours after all: we are made of quanta and immersed into them… who’s influencing who? Is there a serious quantum impact on our society? These are just funny ways to try to relate the microscopic world (in which entanglement has probably nothing to do with love) to the world in which we are used to live. Everybody may imagine the situation which in his fantasy best applies to this strange quantum realm. Already at the ages of Romans and Greeks, people invented figures (gods) associated to natural events, and pictured them as banqueting and being involved in love affairs. Entanglement is surely one of the mysterious ‘gods’ of the Book of Nature as we know it today, and “when it comes to entanglement – according to V. Vedral – we’ve only just discovered the tip of an iceberg”. I conclude by hinting at what entanglement can really do for us. Apart from its quite interesting social aspects at the microscopic level, the new technological quantum information revolution is taking place, based on entanglement and its properties. In particular, Alice and Bob can send flirting emails to each other with the unconditional security that nobody can eavesdrop, as they encrypt their data via a secret key established from the intrinsic randomness of quantum particles, and protected by the monogamy of entanglement. And this is reality: quantum cryptosystems are plugand-play devices which you can buy from MagiQ <www.magiqtech.com/> or IdQuantique <www.idquantique.com>, and install on your PC to definitely solve the problem of (quantum) hackers. Similarly, we are working to build quantum computers, which exploit quantum superpositions (wave and particle, dead and alive..) to do parallel calculations billions of times faster than current supercomputers!!! And there is much, much more… I’ve enjoyed speaking about one particular aspect of science, which is entering into and gradually affecting popular culture. Like this, there are many others. Now, next time you meet a theoretical physicist, please don’t look at him in that strange way :) and remember … we are all entangled!